It depends on which system your jeweler uses to create their molds. If they hand carve a master plug, a simple sketch of the design will allow the plug artist to create a master. But you would be relying on that persons artistic talent to render your sketch into a 3D hard copy.
If they use some form of 3axis computer to create the plug they will need a design compatible with their computer. This is usually an MS Illustrator design.

I am currently doing much the same for an idea I've been toying with for a couple of months. The people who will do the actual casting are in Scotland so I will be sending them a full scale badge which I am carving. They will then use their CAD machine to enter the design into their computer which will create the molds.